TFG: Development of an evaluation device for wireless networks on the body

B105 Electronic Systems Lab, of the Electronic Engineering Department, developed in the past several nodes called ‘Yetimote’, which work on the ISM frequencies of 433 MHz, 868 MHz and 2.4 GHz. During the last years, one of the main target’s laboratory has been the study of wireless networks over the human body (WBAN), composed by sensor nodes that are placed on different points of such human body to collect data for several purposes, usually for medical applications. However, the Yetimote node is addressed to use traditional wireless networks (WSN), due to its size and specific physical format.

The objective of this project was to adapt this node for evaluating and developing WBAN networks. To achieve this goal, one of the main printed circuit boards of the Yetimote node, called Cerberus, which is in fact the part in charge of carrying the wireless communications out, has been modified to make it more wearable.

On the other hand, the context of the project has been analyzed in more detail, describing WBAN networks in depth, the most common characteristics of these networks and their different usages. After a detailed analysis of the requirements to be fulfilled by the new board to be designed in the context of this work, a very deep study has been carried out about possible antennas to be used in this new solution. Finally, the specific choice of the antenna to be used in this work for each band was determined based on its characteristics. One of the electronic components which humans are more accustomed to is a wristwatch, so the PCB has been designed to be integrated inside an enclosure with this shape.

The next step was the electronic design and the PCB implementation of the new board called ‘Mini-Cerberus’, which has been designed using the Altium Designer tool. This new PCB will be connected to the rest of the Yetimote node through the board ‘Auxiliar’ which will be connected to the ‘Mini-Cerberus’ PCB through a flat cable. In addition, the ‘Mini-Cerberus’ board has several versions, one of them has a Pi-Network for each frequency band. Finally, the components were assembled using an industrial furnace and by manual welding. In the figure below, the previous ‘Cerberus’ PCB is shown in front of the new ‘Mini Cerberus’ prototype.

Additionally, some trials have been carried out in real environments to verify the correct operation of the developed design. Several tests have been performed in different real-world scenarios to study the performance of the new Mini-Cerberus board for different frequencies and transmission power values, and these results have been compared with those obtained for the original Cerberus board, which was used as reference or baseline.

In conclusion, it can be affirmed that the new ‘Mini-Cerberus’ PCB has a better performance in WBAN scenarios in the 433 MHz frequency band, while the 2,4 GHz frequency band has the worst performance of those studied. In relation to the Cerberus board, the new prototype has a lower performance compared to the original model, but this is an expected result due to the modifications made for its miniaturization


This work is part of the ROBIM project in which the working group B105 Electronic Systems Lab of the University Universidad Politécnica de Madrid collaborates. The ROBIM project takes part in the program Programa Estratégico CIEN with the support of the CDTI (Centro para el desarrollo tecnológico Industrial) and the RDF (Regional Development Forum) for Europe.

The ROBIM project seeks to automate technical inspections of buildings, reducing costs and execution times associated with these processes. The system makes use of a drone for inspection work, thus avoiding the installation of scaffolding and all the security measures that the process requires, which is costly in time and money. Currently, the drone has a communication channel that allows users to obtain information on the process, as well as direct the drone whenever necessary.
The main objective of this work is to create a secondary, safe and effective communication channel, for situations where communication with the main system is not possible. To achieve this, the project stablish the following requierements:

– The device must allow radiocommunication in ISM bands.
– The device has an USB interface to connect with the computer/drone.
– The communication must be reliable by allowing communication throwgh various channels and implementing software-defined radio and cognitive radio.

Therefore, to achieve these objectives, this work proposes the design of a 2-channel device for radiocommunication in the 433 MHz and 868 MHz bands, using two SPIRIT1 transceivers and an ARM Cortex-M4 microcontroller.

Picture of the device’s high-level design

The Hardware design has been made usign the Altium Designer PCB design layout tool . The designed PCB is divided into three parts: the power/communication stage, the control stage with the microcontroller and the radiofrecuency stage with both SPIRIT1 trasnceivers.

Picture of the 3D reconstruction of the board designed in Altium Design tool

The software design has been developed in 2 stages: software design of an application for evaluation boards during the PCB manufacturating process and software design of a final application for the designed PCB.
For the software design of evaluation board, the NUCLEO – L053R8 with the X-NUCLEO-IDS01A4 radio frequency module has been chosen, which allows radio communication in the 868 MHz band. The final design of the software is based on the software of the evaluation board but improving its functionality by adding communication through two channels with a cognitive procedure based on the CSMA / CA protocol and implementing serial communication with the user.

The application designed for the device allows, then, a cognitive communication based on CSMA/CA protocol in bands 433 MHz and 868 MHz in addition to communication with the user and the drone enabling the possibility of the implementation of the second channel for the communication with the drone.

B105 Radar Sensor Developments


Radar technology is a well-known field used since 1940s. This technology has been traditionally applied in military and aerospace fields while it has not been highly exploited in civil applications. However, in the last years, radar transceivers cost-reduction and miniaturization have allowed its application in other fields such as traffic and vehicular safety.

These low-cost radar sensors uses the Doppler effect to obtain information about obstacles or targets in its range. The radar transmits a signal and the frequency shift of the returned signal provides the velocity of the moving targets. There are two main operating modes for these radar sensors:

  • Unmodulated Doppler radar. This operating mode is the most commonly used. The hardware and processing software needed is quite simple which allows using these sensors in size-constraint and resource-contraint devices. However, they only provide velocity information of moving objects in its range. That means that static objects are missed, the distance of the objects cannot be obtained, and two objects moving at the same velocity will be detected as one.
  • Frequency Modulated Continuous Wave (FMCW) radar. This operating mode is used to obtain the distance of static and moving objects. The radar signal is frequency modulated -usually with a frequency ramp- to allow obtaining distances and velocities from the returning signal frequency shift. Thereby, it is necessary to generate a signal to realize the frequency modulation which increases the hardware complexity. Besides, the software processing is harder as there are much more information to process and there are more noise sources from unwanted environment targets.

In B105 Electronic Systems Lab we have developed a full radar system that can operate in both modes and includes all the hardware and the software necessary. This radar system is being used for traffic safety and traffic monitoring applications in several research projects.